/** caller handles locking */
static bool PREPLOGBUFFER(AlignedBuilder& bb) {
bb.reset();
unsigned *lenInBlockHeader;
{
// JSectHeader
bb.appendStr("\nHH\n", false);
lenInBlockHeader = (unsigned *) bb.skip(4);
}
string lastFilePath;
{
scoped_lock lk(privateViews._mutex());
for( vector<WriteIntent>::iterator i = wi._writes.begin(); i != wi._writes.end(); i++ ) {
size_t ofs;
MongoMMF *mmf = privateViews._find(i->p, ofs);
if( mmf == 0 ) {
journalingFailure("view pointer cannot be resolved");
}
else {
if( !mmf->dirty() )
mmf->dirty() = true; // usually it will already be dirty so don't bother writing then
{
size_t ofs = ((char *)i->p) - ((char*)mmf->getView().p);
i->w_ptr = ((char*)mmf->view_write()) + ofs;
}
if( mmf->filePath() != lastFilePath ) {
lastFilePath = mmf->filePath();
JDbContext c;
bb.appendStruct(c);
bb.appendStr(lastFilePath);
}
JEntry e;
e.len = i->len;
e.fileNo = mmf->fileSuffixNo();
bb.appendStruct(e);
bb.appendBuf(i->p, i->len);
}
}
}
{
JSectFooter f;
f.hash = 0;
bb.appendStruct(f);
}
{
unsigned L = (bb.len() + 8191) & 0xffffe000; // fill to alignment
dassert( L >= (unsigned) bb.len() );
*lenInBlockHeader = L;
unsigned padding = L - bb.len();
bb.skip(padding);
dassert( bb.len() % 8192 == 0 );
}
return true;
}
/** put the basic write operation into the buffer (bb) to be journaled */
static void prepBasicWrite_inlock(AlignedBuilder&bb, const WriteIntent *i, RelativePath& lastDbPath) {
size_t ofs = 1;
MongoMMF *mmf = findMMF_inlock(i->start(), /*out*/ofs);
if( unlikely(!mmf->willNeedRemap()) ) {
// tag this mmf as needed a remap of its private view later.
// usually it will already be dirty/already set, so we do the if above first
// to avoid possibility of cpu cache line contention
mmf->willNeedRemap() = true;
}
// since we have already looked up the mmf, we go ahead and remember the write view location
// so we don't have to find the MongoMMF again later in WRITETODATAFILES()
//
// this was for WRITETODATAFILES_Impl2 so commented out now
//
/*
dassert( i->w_ptr == 0 );
i->w_ptr = ((char*)mmf->view_write()) + ofs;
*/
JEntry e;
e.len = min(i->length(), (unsigned)(mmf->length() - ofs)); //dont write past end of file
assert( ofs <= 0x80000000 );
e.ofs = (unsigned) ofs;
e.setFileNo( mmf->fileSuffixNo() );
if( mmf->relativePath() == local ) {
e.setLocalDbContextBit();
}
else if( mmf->relativePath() != lastDbPath ) {
lastDbPath = mmf->relativePath();
JDbContext c;
bb.appendStruct(c);
bb.appendStr(lastDbPath.toString());
}
bb.appendStruct(e);
#if defined(_EXPERIMENTAL)
i->ofsInJournalBuffer = bb.len();
#endif
bb.appendBuf(i->start(), e.len);
if (unlikely(e.len != (unsigned)i->length())) {
log() << "journal info splitting prepBasicWrite at boundary" << endl;
// This only happens if we write to the last byte in a file and
// the fist byte in another file that is mapped adjacently. I
// think most OSs leave at least a one page gap between
// mappings, but better to be safe.
WriteIntent next ((char*)i->start() + e.len, i->length() - e.len);
prepBasicWrite_inlock(bb, &next, lastDbPath);
}
}